The use of nicotine substitutes (nicotine gum, patches or inhalers) during the first 12 weeks of pregnancy slightly increases the risk of birth defects, according to a large study of pregnant women and their offspring.

Dr. Maria M. Morales-Suarez-Varela, from the University of Valencia in Spain, and others interviewed 76,768 women between weeks 11 and 25 of pregnancy regarding their smoking habits and use of nicotine replacement products during the first 12 weeks.

There were 20,603 pregnancies resulting in live births of mothers who smoked cigarettes and 56,165 among mothers who did not smoke.

The authors observed a "relative prevalence rate ratio" or RPR, of 1.1 for all congenital malformations among smokers. The RPR for cleft lip or malformations of the digestive system or circulatory system ranged between 1.2 and 1.5.

Among nonsmokers who used nicotine substitutes during the first 12 weeks, the RPR for birth defects was higher — 1.61 — compared with nonsmokers who did not use nicotine substitutes. The RPR for musculoskeletal type malformations was 2.63.

To explain these discrepancies, the researchers offer that nicotine substitutes may be absorbed by a different route and reach higher peak doses of nicotine compared with tobacco smoke.

Even though their study failed to find increased malformation risk among smokers, the researchers say that "there is sufficient evidence for a harmful, overall fetotoxic effect of smoking to warn pregnant women not to smoke at all during pregnancy."

They recommend further study to confirm the potential role of nicotine substitutes in causing congenital malformations.

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